- Boost - lists.boost.org

Reflection?
by Jean-Louis Leroy 06 Nov '08

06 Nov '08

Is runtime reflection going to be available in boost soon? The last I have found on the subject is http://lists.boost.org/Archives/boost/2007/08/126006.php but I see nothing in the sandbox nor the vault. I have toyed with an implementation myself. It supports member variables and functions, multiple and virtual inheritance and object creation. Here is what it looks like. First a small hierarchy: class animal { /* ... */ }; class mammal : public virtual animal { /* ... */ }; class carnivore : public virtual animal{ /* ... */ }; class dog : public mammal, public carnivore{ /* ... */ }; Reflection info is filled like this: reflection_class<animal>::name("animal"); reflection_class<animal>::variable("age", &animal::age); // etc reflection_class<mammal>::name("mammal"); reflection_class<mammal>::base<animal>(virtual_); // etc reflection_class<carnivore>::name("carnivore"); reflection_class<carnivore>::base<animal>(virtual_); // etc reflection_class<dog>::name("dog"); reflection_class<dog>::base<mammal>(); reflection_class<dog>::base<carnivore>(); // a function reflection_class<dog>::function("bark", &dog::bark); // overloaded functions reflection_class<dog>::function<string (dog::*)(void) const>("name", &dog::name); reflection_class<dog>::function<void (dog::*)(const string&)>("name", &dog::name); // constructor reflection_class<dog>::constructor<void* (*)()>(); // etc And here how it's used: animal* pa(new dog); object o(downcast(pa)); // recover dynamic type // access member variable inherited from virtual base `animal' member_variable<int> dog_age(o, "age"); int age = o[dog_age]; // call member function member_function<string (object::*)() const> dog_name(o, "name"); string name = o[dog_name](); // create a dog using default ctor object o("dog"); Ok, there is a bit more to it (e.g. support macros, ambiguity detection, handling of shadowed members, overloaded ctors) but the important part is shown above. All in all it is a foundation upon which one can build multimethods, generic object processing (like Perl's data::Dumper), serialization, object-relational mapping and all sorts of nice tools. Does anybody see interest in this work? Jean-Louis

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Is Boost.Astronomy feasible?
by Mika Heiskanen 06 Nov '08

06 Nov '08

Hello, I would like to think that it would be possible to create a library for common astronomical calculations, and I think boost might be the proper place to create one for the C++ community. First a definition: by common calculations I mean those most relevant to every dat life. For normal people this would pretty much exclude most astronomical calculations except those concerning the sun and the moon. Some examples on what calculations I think would be common are: o sunrise, sunset, noon o sun elevation, azimuth, declination o length of the day o phase of the moon, and whether the visible fraction is increasing or not However, there are some complications: o There are several ways to define twilight times, for example civil, nautical and astronomical. o The sun may set/rise more than once during a day in polar regions, or it may do neither. o What is the definition for the length of the day if sunrise/sunset occurs more than once during a day? o Are separate methods needed for testing whether the given date is of type "polar day" or "polar night" or "midnight sun"? The definitions for the three seem to be a bit ambiguous. For example, it is perfectly possible for the sun to be up at midnight but still to set during the day, in which case you would have "midnight sun" but not necessarily a "polar day", when the sun shines 24h. o Most calculations are intimately tied to the local time, so the API should rely on Boost.Date_time. Many places refer to Meeus's work for the most accurate calculations. The formulas have been ported to C++ in the form of the AA++ (astronomical algorithms) library. However, the library seems to be aimed for experts and there are no easy recipies for solving the common problems mentioned above. The questions I would like to pose are then: o Would a boost::astronomy namespace as implied above be a good addition to boost? o Are there any experts out there who understand the subject matter well enough to provide a robust implementation or atleast guidance on the matter? For example, NOAA provides web based solar position and sunrise calculators. According to the documentation the calculators are based on the work of Meeus. However, there are some clear design issues on how things should be handled in C++ versus the JavaScript embedded into the NOAA pages. Any thoughts on the matter? Regards, --> Mika Heiskanen

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[c++0x] Boost implementations of C++0x standard library components?
by Beman Dawes 05 Nov '08

05 Nov '08

I want to submit an improved timer to Boost. I'd like it to use the C++0x standard library's <chrono> and <ratio> headers. Because it will be many years before such C++0x are universally available, I think Boost should include an implementation of these libraries. Howard Hinnant has kindly contributed his demo implementation of <chrono> and <ratio> as a starting point, so the hard stuff is already done. I'm starting to boostify his code. That brings up questions of header and namespace names. Presumably what we do with these two small headers will set the pattern for any other C++0x standard library headers we include in Boost. Here is a strawman proposal for how we organize C++0x standard library components we choose to add to Boost: * Such libraries go through the regular formal review process, although it will need to be adjusted a bit since the interface is already known and frozen. * C++0x standard library header naming convention is followed. Thus these will be named <chrono> and <ratio> rather than <chrono.hpp> and <ratio.hpp>. * C++0x standard library namespaces are used. Thus namespace std and std::chrono rather than boost and boost::chrono. * Directory structure: boost-root boost c++0x // <ratio>, <chrono>, and other c++0x std lib headers go here ... libs c++0x chrono build doc src // if needed test ratio build doc src // if needed test ... This allows a user to refer to say the ratio header as <boost/c++/ratio>, <c++/ratio>, or just plain <ratio>. The user would have to provide an additional include path of boost-root/boost or boost-root/boost/c++0x for the second and third usages to work. Comments? --Beman

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[MultiIndex] interface comments
by David Abrahams 05 Nov '08

05 Nov '08

Just reading through the docs for this very useful library and I had a few notes: 0. The term /typelist/ (italicized) is used in the tutorial without definition. Do you mean an MPL type sequence, or something else? 1. Seems like the tags functionality could take advantage of Boost.Parameter to provide a nicer interface and save some code. 2. The "shortcuts" save exactly 1 character. Each index of a multi_index_container uses its own iterator types, which are different from those of another indices. As is the rule with STL containers, these iterators are defined as nested types of the index: employee_set::nth_index<1>::type::iterator it= es.get<1>().find("Judy Smith"); <snip> Additionally, multi_index_containers provide shortcut definitions to the iterator types of their constituent indices: employee_set::nth_index_iterator<1>::type it= es.get<1>().find("Judy Smith"); There is a variation of the expression above for use with tags: employee_set::index_iterator<name>::type it= es.get<name>().find("Judy Smith"); // get<1> would also work Notice the column in which "it" appears in both versions. IMO these interfaces should be deprecated (i.e. not documented, and eventually removed) as they provide no readability advantage, hurt learnability, and complicate usage. Regards, -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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[threadpool] recursive fork/join (fibers removed)
by k-oli＠gmx.de 05 Nov '08

05 Nov '08

Hello, http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost-… I've uploaded a new version of threadpool - fibers are remove so that fork/join is provided via recursive execution of sub-tasks (enqueued in local worker-queue). One open item is the synchronization of parent-task und sub-task (signaling via condition variables) - maybe solveable via fibers. regards, Oliver

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Is there any need for a math library doing vectors and matrices operations?
by Christophe Riccio 05 Nov '08

05 Nov '08

Hi, For a 3D programmers using vectors and matrices is as common as using integers. Actually, it's probably even more common! For this reason, every 3D programmer relies on a math library but as they usually don't need much … they implement their own basic math library and that fine. However, most of the time a single graphics software could uses several math libraries because it uses several external libraries that each of them use there own math library. It involves: - A lot of unnecessary copy and conversion of data. - Different meanings for overloaded operators. - Unspecified conventions: row major matrix, column major matrix, left or right handed? - Use of poor math libraries. - Several libraries to understand, to learn: a waste of time for trivial and common need! GPU programmers get some really convenient languages to do graphics on GPU. Cg: http://developer.download.nvidia.com/cg/Cg_2.0/2.1.0012/Cg-2.1_October2008_… HLSL: http://msdn.microsoft.com/en-us/library/bb509561(VS.85).aspx<http://msdn.microsoft.com/en-us/library/bb509561%28VS.85%29.aspx> GLSL: http://www.opengl.org/registry/doc/GLSLangSpec.Full.1.30.08.withchanges.pdf These languages are the result of a lot of experimented developers in 3D graphics and are basically the same. I decided to build a C++ math library based on all the rules that those developers agreed to be good rules and it result in GLM: http://glm.g-truc.net. However, those GPU languages provide good features but limited features: No quaternion, no transformation, lot of limitation on types and rules that couldn't apply directly in C++ (swizzle operators). GLM has limitations because it results of too few developers to think about it. I would like to get more feedback and makes it even more useful. I would lie to making it better find more agreement so that one day it could be ready to be integrated to Boost and hopefully to C++ standard. I'm afraid that such kind of library already have been submitted and rejected, I know it need more work but I believe on my approach and I'm not afraid to change the library so that everyone agree it's good. Thanks, Christophe Riccio

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[Boost.Build] boost.python tutorial is not compiling
by Sandeep Gupta 05 Nov '08

05 Nov '08

Hi, I am reasonably sure that this is due to omission in the configuration file. I checkout from the trunk and all compilation went without problem. But the hello world example within the boost.python is failing with error: LINK : fatal error LNK1104: cannot open file 'boost_python-vc80-mt-gd-1_38. lib' call "f:\Program Files\Microsoft Visual Studio 8\VC\vcvarsall.bat" x86 >nul link /NOLOGO /INCREMENTAL:NO /DLL /DEBUG /subsystem:console /out:"bin\msvc-8.0\debug\hello_ext.pyd" /IMPLIB:"bin\msvc-8.0\debug\hello_ext.lib" /LIBPATH:"F:\CodeBase\Libs\Python-2.5.2\PCbuild8\win32release" @"bin\msvc-8.0\debug\hello_ext.pyd.rsp" .... .... >From what I can make that LIBPATH doesn't have path to boost_python-vc80-mt-gd-1_38.lib. The lib in question is build at its requisite place. Appreciate any help. Thanks sandeep

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[uuid] width
by Kenneth Laskoski 05 Nov '08

05 Nov '08

Hello, I was reading/using/copying your code when I spotted a possible bug in the inserter operator<<. The standard result for built-in types is to align the output and set the ostream width property back to zero, which does not happen when I use your class. For example: int main() { uuid x; cout << 'a' << setw(40) << x << 'a' << endl; } output is a00000000-0000-0000-0000-000000000000 a but should be a 00000000-0000-0000-0000-000000000000a If this is the intended behavior, please document it. If not, maybe the attached patch will help put things back on rail. Regards, Kenneth

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[thread] hardware_concurrency() not working on all platforms?
by Oliver Kowalke 05 Nov '08

05 Nov '08

Hello, boost::thread::hardware_concurrency() seams not to work on all platforms (xBSD, OpenSolaris). Is there some ongoing work to provide this functionaly on the other platforms too? regards, Oliver -- Der GMX SmartSurfer hilft bis zu 70% Ihrer Onlinekosten zu sparen! Ideal für Modem und ISDN: http://www.gmx.net/de/go/smartsurfer

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Boost.Build changes for 1.38
by Vladimir Prus 04 Nov '08

04 Nov '08

As we're nearing 1.37, and the time for big changes that follows after, I wanted to discuss one Boost.Build change I want to make. Right now, we have two ways to build Boost -- using bjam directly, and using configure and make (which are wrappers over boost.build). The first approach may be a bit hard, and the second is very nice when it works, but it leads to other problems: - users start to assume it's "real" configure, and get upset when various variables that CXXFLAGS have no effect - if users want to do anything custom, like mingw cross compilation, they have to go back to direct use of bjam anyway. So, I'd like to suggest a solution where building of boost involves three steps: 1. ./bootstrap.sh or ./bootstrap.bat This step just builds bjam and puts it into boost root 2. ./bjam [--build-type=complete] [--layout=xxx] [properties] configure This step: - Tries to detect what compilers you have - Figures which optional libraries you have, and which you don't (e.g. ICU) - Writes a file project-config.jam with all the discovered information. 3. ./bjam This step can be usually invoked with no parameters, reads the configuration information from project-config.jam, and builds everything. For new users, this solution is only marginally more complex that configure/make, and does not create the false impression it's autoconf. For power users, the file produced in (2) can be tweaked and extra options can be specified in (3). For all users, this means that various properties can be specified only once in (2) and need not be repeated on every build, which is clearly a convenient thing. Anybody has comments about this plan? - Volodya -- Vladimir Prus http://vladimir_prus.blogspot.com Boost.Build V2: http://boost.org/boost-build2

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